The present invention relates to an edible, oil-in-water type emulsion having rheological and sensorial properties resembling those of mayonnaise, but which emulsion has a reduced content of oil.
Traditional mayonnaise is an oil-in-water type emulsion comprising vegetable oil (70-80%), egg yolk (5-8%), salt, vinegar (to achieve a pH of the water phase of about 4-4.5), mustard, and optionally sugar, pepper and herbs. The oil is generally present as droplets (average size 4-8 xcexcm) dispersed in a water phase. Following the droplet size and the high amount of dispersed phase, a very close packing is obtained. As a result of the close packing and the thin layers of continuous phase separating them, the typical rheological behavior (by consumers perceived as thickness) of mayonnaise is obtained. This is reflected by e.g. a Stevens value of about 80 to 120 (speed 2 mm/s, distance 20 mm, using a typical mayonnaise grid: mesh 7, thread thickness 0.8 mm, mesh width 2.83 mm, see FIGS. 1a and 1b, for the grid when mounted, and the grid itself, respectively).
There is, however, an ever-increasing demand for mayonnaise-type products having a lower content of oil but otherwise still having good sensorial properties and mouthfeel, as are associated with full-fat mayonnaise.
Lowering the content of oil in an otherwise standard mayonnaise-type formulation and processing will result in less dense packing of oil droplets in the continuous phase. As a result of this the formulation will have a dramatically lowered thickness or viscosity as a result, following which it will no longer be spoonable etcetera, and not be acceptable as a mayonnaise-type product.
A solution to this can be to add thickeners to the water phase, such as gums and/or starch. The use of such thickeners can affect flavour and/or mouthfeel. The use of starch can lead to sticky, chewy products.
Another solution to the above problem is to rigorously decrease the size of the oil droplets that are dispersed in the continuous phase. When the droplets are very small (around or less than 1 xcexcm), and the amount of oil is not very low, this may give good result. A disadvantage, although specific equipment will be needed in order to get the extremely small droplets. Disadvantages of this solution is that these very small droplets are very difficult to obtain, as extremely high shear will be needed to obtain the small droplets and the need for additional compounds in order to stabilize the small droplets (the normal amount of 5-8% egg yolk will not be sufficient). An example of this technology has been described in JP 06/054,662 (Kao Corp.). In this reference, an emulsion is disclosed of 10-60% oil in 90-40% water phase, wherein the aqueous phase contains at least one protein in an amount of 1-10% by weight, and wherein not less than 80% of the oil droplets in the emulsion has a particles size not larger than 1 xcexcm (i.e. at least 80% of the oil droplets is equal to or smaller than 1 xcexcm). Preferably, the particle size is in the range of 0.1-1.0 xcexcm. Proteins reported in said reference to be suitable are egg protein, soybean protein, milk protein, and single proteins isolated therefrom. Disclosed examples use ultra high-pressure homogenisers operating at 600 bars for preparation.
JP 63/181,972 (Sonton Shokuhin KK) discloses the use of whey protein concentrates (WPC) for emulsification of acidic oil-in-water type emulsified food products. WPC is used over other protein-containing emulsifiers because of its heat resistance and shape holding ability, in the application as filling/topping on/in bread.
EP 788747 (Nestle) relates to a mayonnaise-like product containing 55-85% oil, and which contains another emulsifier than egg yolk. The compositions according to this reference contain as emulsifier at least 0.1% milk proteins or vegetable proteins, which proteins are heat-denatured to a degree of 70-80%. The denaturation is said to be necessary to obtain a mayonnaise-like product and to avoid gel formation.
Hence, there is a need for an edible, mayonnaise-like product with a lower amount of oil than conventional mayonnaise, which product resembles (part of) the Theological behavior and/or appearance of full-fat mayonnaise. Preferably, this can be obtained without using starch-based thickeners.
It has now been found that the above can be achieved by an edible composition comprising an oil-in-water emulsion comprising:
35-70% by weight edible oil,
0.5-10% by weight egg yolk derived emulsifier,
0.3-1.5% by weight casein,
65-25% water,
wherein at least 60% of the oil droplets has a size of 1-5 xcexcm.
The above composition has preferably a Stevens value of 60-160, preferably 75-140 (when measured at 20xc2x0 C., after 2 weeks storage at 20xc2x0 C., speed 2 mm/s, distance 20 mm, mayonnaise grid (mesh 7, thread thickness 0.8 mm, mesh width 2.83 mm, see FIGS. 1a and 1b, for the grid when mounted, and the grid itself, respectively).
Emulsification is preferably obtained using a high-pressure homogeniser operating at a pressure of less than 600 bars, more preferably less than 400 bars. There is no need for very small droplets, which can only be obtained using specific equipment (e.g. ultra high-pressure homogenisers operating at 600 bar). Suitable pressures are in the range of 50 to 300 bars, e.g. 100 or 200 bars.
In such a composition, casein, unlike other proteins, seems to perform a unique function. Without wishing to be bound by theory, it is believed the properties of the casein are such that under the conditions as are specific for mayonnaise (pH 3.0-5.0) and in the presence of oil droplets of a suitable size, aggregates or clusters can be formed in which a casein xe2x80x9cparticlesxe2x80x9d are surrounded by various oil droplets, as can be shown by micrographs. Without wishing to be bound by any theory, the so-formed clusters have apparently a thickening effect on the emulsion. This thickening effect (which surprisingly does not result in elastic properties, which are undesired) is such that with a reduced amount of oil, an increased level of water and the addition of an effective amount of casein, a product can be obtained with a very much similar appearance and/or Theological behavior (e.g. spoonable character) as standard mayonnaise.
In the compositions according to the invention, the droplet size is somewhat smaller than for conventional mayonnaise (about 4-8 xcexcm), but not as small as in techniques as are described in the prior art (e.g. JP 06/054662: 0.1-1 xcexcm). Due to the majority of the oil droplets being xe2x80x9cclusteredxe2x80x9d around the casein particles, many conventional droplet-size measurement techniques are not very suitable. A technique that is suitable is computerised image analysis of micrographs.
With respect to casein, it is submitted that this particular protein seems to behave in a specific way, thus enabling the xe2x80x9cclusteringxe2x80x9d to occur. This implies that (majority of) the casein would be present as globules with part of the oil droplets clustered on the surface of the casein globules. Part of the oil droplets would then not be clustered with the protein globules, but emulsified in the aqueous phase.
It is submitted that replacing casein with e.g. whey protein does not result in said clustering. This may be due to the different structure of the proteins. Casein is under mayonnaise conditions (e.g. pH 4.0-4.8) present in a random coil form or in other words as a disorganised, insoluble protein. Whey protein on the other hand, is a globular, soluble protein, which unfolds under heating. Excessive heating will cause denaturation. Neither before nor after denaturation will the whey protein be capable of forming clusters with oil droplets. Following this, the presence of casein is essential in the present invention. However, a small amount of whey protein (next to casein) is not detrimental. Hence, instead of pure casein protein, it is possible to use skimmed milk protein (SMP), which is a commercially available product, usually consisting of about 35% protein, of which about 80% is casein and about 20% is whey. Casein is preferably not heat denatured. Like SMP, buttermilk protein (BMP) may be used.